sensitivity

So my dog Dudley is 13 years old. He's always had good health and only needed to go to the vet once in his whole life and that was for a minor cut on his paw. Over the past week or so I have noticed his back legs kicking out. This happens when I touch (even sightly) the spinal area on his back...

I have a 5 month old puppy who it seems has a sensitive stomach. She was on Purina Smart Blend from breeder until up to 4 months. She was constantly having loose stools and BAD gas so we switched her to Wellness Large Breed Puppy. Her stools seem inconsistent; some very good, others VERY loose...

Anyone try this yet? Welcome to Nutriscan - Dog Food Sensitivity Kit There's a difference between food allergy and sensitivities...supposedly this test can tell you their sensitivities from a saliva swab